The invention relates to a limiting circuit breaker with a molded insulating case, comprising in each pole:
an electrodynamic repulsion contact system having a conducting support arm equipped with a first contact, and a movable contact having at least a second contact cooperating in the closed position with the first contact, said movable contact being driven to the open position by electrodynamic forces generated during a first repulsion phase after the current has exceeded a preset threshold, PA1 and an electromagnetic anti-fall latch capable of occupying an active position to temporarily keep the movable contact open after repulsion.
An electromagnetic anti-fall latch for a limiting circuit breaker is already known from the documents U.S. Pat. No. 4,409,573, DE-OS No. 1,463,310 and FR-A No. 2,272,479. Actuation of the latch to the active position results from the intervention of electromagnetic attraction forces generated by a strong current flowing in the pole.
According to the document U.S. Pat. No. 4,409,573, the latch is formed by a latching blade capable of cooperating with a notch provided at one of the ends of the movable contact arm on the bar side. The distance between the latch and the contact parts between which the arc is established makes it necessary to fit a steel ring surrounding the bar to strengthen the electromagnetic attraction effect on the latch.
The latching effect of the movable contact in the repelled position has the drawback of preventing any possibility of selectivity in the circuit. Unlatching is achieved by rotation of the bar after tripping of the mechanism.
Another anti-fall device (see document U.S. Pat. No. 4,612,430) uses a different technique implementing the acceleration of the movable contact when electrodynamic repulsion occurs to act initially by mechanical effect on the latch, which is then completely attracted to the active position by magnetic attraction.
The object of the invention consists in improving the achievement of an electromagnetic anti-fall latch for a limiting circuit breaker.